Long Term Goals: Serenix Pharmaceuticals (SP) will develop drugs for the treatment of CNS disorders. Strategy: SP acquired a series of vasopressin receptor antagonists from Eli Lilly and Company and has refined these molecules through manipulations of various structural zones. A subset of these antagonists (LEAD SERIES) exhibit reasonable affinity for the vasopressin receptor subtype involved in depression and stress-related affective disorders. The LEAD SERIES requires refinement to optimize affinity (less than 5 .0 nM) and early stage testing to demonstrate biological activity. The platform molecule has four essential structural zones; two of these will be the focus of the proposed research. Phase I objectives are (i) utilize classical and combinatorial chemistry to modify structural zones on the LEAD SERIES to generate ca. 200 compounds, (ii) screen these for target receptor affinity and focus on those with Kds less than 5 nM, and (iii) test the high affinity compounds for in vitro biological activity. The findings, combined with considerations related to affinity, structural diversity, structural attractiveness, and QSAR models, will identify promising compounds for testing in Phase II for oral absorption, stability, metabolism, toxicity, and efficacy. PROPOSED COMMERCIAL APPLICATION: SP will focus on the development of a novel drug for the treatment of depression and stress-related affective disorders. In 1999, the NIMH reported that depression affects over 19,000,000 adults in the United States, making it the most common serious CNS disease. The proposed drug represents a novel pharmacological approach that differs from the tricyclics, SSRIs, and NRIs currently used for these disorders. It therefore may capture significant market share.